Opioid substitution therapy as a strategy to reduce deaths in prison: retrospective cohort study

Objectives To describe deaths in prison among opioid-dependent people, and examine associations between receipt of opioid substitution therapy (OST) and risk of death in prison. Design Retrospective cohort study. Setting Adult prisons in New South Wales (NSW), Australia. Participants 16715 opioid-dependent people who were received to prison between 2000 and 2012. Interventions Opioid substitution therapy. Primary outcome measures Natural and unnatural (suicide, drug-induced, violent and other injury) deaths in prison. Results Cohort members were in prison for 30998 person-years (PY), during which time there were 51 deaths. The all-cause crude mortality rate (CMR) in prison was 1.6/1000 PY (95% CI 1.2 to 2.2/1000 PY), and the unnatural death CMR was 1.1/1000 PY (95% CI 0.8 to 1.6/1000 PY). Compared to time out of OST, the hazard of all-cause death was 74% lower while in OST (adjusted HR (AHR): 0.26; 95% CI 0.13 to 0.50), and the hazard of unnatural death was 87% lower while in OST (AHR: 0.13; 95% CI 0.05 to 0.35). The all-cause and unnatural death CMRs during the first 4weeks of incarceration were 6.6/1000 PY (95% CI 3.8 to 10.6/1000 PY) and 5.5/1000 PY (95% CI 2.9 to 9.4/1000 PY), respectively. Compared to periods not in OST, the hazard of all-cause death during the first 4weeks of incarceration was 94% lower while in OST (AHR: 0.06; 95% CI 0.01 to 0.48), and the hazard of unnatural death was 93% lower while in OST (AHR: 0.07; 95% CI 0.01 to 0.53). Conclusions Mortality of opioid-dependent prisoners was significantly lower while in receipt of OST.